He was jailed for 23 years, was made subject to a Sexual Harm Prevention Order and must sign the Sex Offenders’ Register for life.

The judge described Grimes’ actions as ‘vile, despicable, and perverted’ and said that they went ‘beyond normal human comprehension’.

In July 2016 Bedfordshire Police received intelligence that an IP address linked to Grimes’ home address was being used to download indecent images of children. A warrant was carried out at the property and a number of devices were seized, including a miniature covert recording device.

The devices were found to contain more than 4,600 indecent images of children and babies, including almost 1,000 of the most severe category.

While investigations were on-going into the indecent image offences, someone contacted the police to say that a young girl had been abused by Grimes in the 1970s. Three further victims of abuse were also identified during the investigation, with the abuse spanning from the 1970s to the 2000s.

Grimes was arrested and charged with 17 offences relating to child sexual abuse.

Investigation Officer Paul Baddeley from the Bedfordshire Police Internet Child Abuse Investigation Team (ICAIT) said: “This is one of the worst cases of child sexual abuse that I have ever dealt with. Grimes sexually abused four young girls on multiple occasions. His abusing then evolved with the digital age with the viewing and creating of horrific indecent images of children and babies.

“Grimes is clearly a very dangerous individual and I’m pleased that he has been locked away for such a significant amount of time. This punishment can never make up for the years of abuse that Grimes inflicted, not to mention the lasting mental anguish caused to his victims, but I hope that those involved can feel comforted by the fact he is now no longer a risk to others in society.

“I’d like to praise the victims for their bravery in speaking out about their abuse and I hope it encourages other victims of sexual abuse to come forward in the confidence that they will be believed and justice can be done - no matter how long ago the abuse took place. I’d also like to pay tribute to the families of the victims who have been amazing in their strength and support.”

In a statement, one of the victims said: “For a long time I practised putting the memories to the back of my mind, pretending like they never happened and like everything was fine, that could not have been further from the truth. I feel embarrassed and humiliated, I am scared that people know and look at me differently.

“Even though I’m scared of writing this and admitting how I truly feel I would like the court and judge to know about me, what I have suffered and what my life is like as a result of the abuse and lies. What happened to me has not eased with time it never will.

“I am a real victim and it affects me every day in one way or another. I have come to live with the fact that I will never be free of this ordeal.”

An NSPCC spokesperson for the East of England said: “Grimes’ horrific campaign of abuse will have left untold suffering on his victims who have showed tremendous courage in speaking out and helping to put him behind bars.

“Sexual abuse is never the fault of the victim. This case shows that people who abuse children have nowhere to hide and survivors will be listened to and supported, no matter how long ago the offences took place.”

To report child sexual abuse, both current and non-recent, call police on 101.